Run multithreaded quiet tests

We historically have run single-threaded verbose tests because we were
faulting all over the place due to bugs in rustc itself, primarily
around calling conventions and passing values around. Those bugs have
all since been fixed so we should be clear to run multithreaded tests
quietly on CI nowadays!

Closes rust-lang#621

Author: alexcrichton

ci/run.sh

@@ -6,7 +6,6 @@ set -ex
 
 # Tests are all super fast anyway, and they fault often enough on travis that
 # having only one thread increases debuggability to be worth it.
-export RUST_TEST_THREADS=1
 #export RUST_BACKTRACE=full
 #export RUST_TEST_NOCAPTURE=1
 
@@ -45,7 +44,7 @@ cargo_test() {
     else
         cmd="$cmd -p coresimd -p stdsimd"
     fi
-    cmd="$cmd -- $2"
+    cmd="$cmd -- $2 --quiet"
     $cmd
 }